DE69620261T2 - ORTHOPEDIC PLASTIC FABRIC WITH HARD AND SOFT AREAS - Google Patents

Description

This invention relates to materials for orthopedic casting.

Background of the invention

Many different orthopedic casting materials have been developed for use in immobilizing broken or otherwise injured limbs. Some of the first casting materials developed for this purpose involved the use of plaster casts, which consisted of a cotton gauze mesh with plaster incorporated into the openings and onto the surface of the mesh. However, there are several disadvantages associated with plaster casts; these include a low strength to weight ratio, resulting in a finished plaster cast that is very heavy and bulky. In addition, plaster casts develop their strength over a relatively long period of time, making it necessary to avoid weight-bearing situations for up to 24 to 48 hours. Furthermore, plaster casts typically disintegrate in water, making it necessary to avoid bathing, showering, or other activities that involve contact with water.

EP-A-0 135 890 describes a process for producing a curable textile fabric in which different areas are selectively curable. The textile fabric comprises a first preconditioned fibre which is knitted or woven together with a second fibre (elastomer) which is under tension and then selectively cured by heating and applying an immobilising agent.

A significant advance in technology was made when it was discovered that synthetic polyisocyanate prepolymers could be used to prepare a resin for materials for orthopedic casting. Typical commercially available synthetic orthopedic casting materials include a knitted glass fiber backing impregnated with a polyisocyanate prepolymer resin. These orthopedic casting materials can provide a significant advance over plaster casts, including a higher strength to weight ratio. However, knitted glass fiber backings of conventional casting articles can become very rough when cured and often result in casts with sharp edges. The sharp edges can cause skin abrasions and/or chafe against clothing, requiring the medical professional to use padding materials around the edges to try to prevent the casting article from contacting the skin.

Brief description of the invention

From the above, it will be seen that there is a need in the art for an orthopedic casting material that has the advantages of synthetic orthopedic casting materials, e.g., a high strength to weight ratio, but without the sharp edges. Such orthopedic casting materials and methods of making them are disclosed and claimed herein.

In general, the orthopedic casting tapes of the present invention comprise a first longitudinally extending portion of a soft casting material and a second longitudinally extending portion of a hard casting material connected to the first portion. The soft and hard casting materials may comprise, for example, soft or hard curable resins associated with a backing, soft or hard thermoplastic materials associated with a backing, or soft or hard extruded casting materials.

In a preferred embodiment, the present invention provides bands for orthopedic casts comprising a carrier and at least one curable resin associated with the backing. The casting tape comprises at least one longitudinally extending portion of a soft casting material and at least one longitudinally extending portion of a hard casting material. Preferably, the longitudinally extending portion of the soft casting material and the longitudinally extending portion of the hard casting material comprise different curable resins. Alternatively, they may comprise two different backings.

The casting tapes most preferably have one or two edge regions of the softer casting material. When wrapped around a limb, the soft edge regions can form a soft edge of the casting tape. For a typical 10 cm wide casting tape, the soft edge regions are preferably at least 0.5 cm wide.

The invention also describes new methods for making orthopedic casting tapes comprising the steps of providing a curable casting tape comprising at least one longitudinally extending region of a soft casting material and at least one longitudinally extending region of a hard casting material; initiating curing of the casting tape (e.g. by exposing the casting tape to water); optionally wrapping the casting tape in such a way that the soft region overlaps one or more edges of the casting tape; and allowing the casting tape to cure to form an orthopedic casting tape.

The invention also describes new production methods for producing these new orthopedic cast bandages. In one embodiment, these new methods include the steps of providing a fabric carrier and applying two different curable resins onto the carrier to form two adjacent longitudinally extending regions of different hardness.

The present invention also provides improved splint articles comprising, for example, a backing and at least one curable resin associated with the backing. Generally, the splint article has a hard central region and at least one soft edge region. The splint may further comprise a thumb hole having a soft edge region surrounding the periphery of the thumb hole.

Definitions

The term "casting material" refers to a material (e.g., a composite, a resin-coated sheet, etc.) that undergoes a change of state from a generally moldable first state to a generally non-moldable second state, allowing the formation of a custom moldable support device. The support devices of the present invention are characterized by having at least one "soft region" and at least one "hard region." The second state of the soft region and the hard region differ in at least one physical property, with the hard region being at least significantly stiffer, less resilient, or harder than the soft region. The term "differential hardness" refers to the relative difference in stiffness, resilience, or hardness between the soft and hard regions of a casting tape or splint (i.e., the relative difference between the respective second states of the two regions).

The term "casting tape" refers to an elongated strip of a casting material. The casting tapes of the present invention may optionally be wound onto a roll prior to use and are characterized by having at least one longitudinally extending "soft region" and at least one longitudinally extending "hard region". The second state of the soft region and the hard region differ in at least a physical property, wherein the hard region is at least noticeably stiffer, less elastic, or harder than the soft region.

The "soft region" of a casting material (e.g., a casting tape or a splint) is that region of the casting material that comprises a soft casting material. The term "soft casting material" preferably refers to a casting material that undergoes a change of state from a generally moldable first state to a second state that comprises a generally semi-rigid, elastic or soft support. The term "soft casting material" includes a soft resin coated onto a backing as well as a soft extruded casting material. The term "soft resin" preferably refers to a curable resin system that forms a generally semi-rigid, elastic or soft support when coated onto a backing or otherwise applied and cured. Most preferably, the soft resin, when applied to the edge of a conventional fiberglass backing and cured, produces an edge that does not cut and/or abrade the wearer's skin or otherwise injure the wearer.

The "hard portion" of a casting material (e.g., a casting tape or a splint) is that portion of the casting material which comprises a hard casting material. The term "hard casting material" preferably refers to a casting material which undergoes a change of state from a generally moldable first state to a second state comprising a generally rigid, inelastic or hard support. The term "hard casting material" includes a hard resin coated on a backing as well as a hard extruded casting material. The term "hard resin" preferably refers to a curable resin system which, when coated or otherwise applied to a backing and cured, forms a generally rigid, inelastic or hard support. Most preferably, the hard resin, when coated on a backing, forms a generally rigid, inelastic or hard support. conventional fiberglass backing, a rigid support device capable of bearing the weight normally borne by the limb around which the support device is wrapped.

The term "curable resin system" refers to any type of resin system that undergoes a change of state from a generally flowable or moldable uncured first state to a generally non-flowable or non-moldable cured second state.

The terms "backing" and "fabric" refer to the structure to which one or more curable resins are coated or otherwise applied. A "fabric backing" is a backing comprising a knitted, woven or nonwoven textile material.

The term "associated with" refers to the intimate relationship between the resin system and the support, as may be achieved, for example, by coating a support with a resin and/or impregnating a support with a resin.

Short description of the drawings

The invention can be better understood by reference to the drawings:

Fig. 1 shows a partially unwound roll of casting tape with two soft areas along each edge of the casting tape;

Fig. 2 shows a partially unwound roll of casting tape with a soft area along one edge of the casting tape;

Fig. 3 shows a partially unwound roll of casting tape with three soft areas along each edge of the casting tape and along the center of the casting tape;

Figure 4 shows a human arm wrapped with the casting tape of the present invention;

Fig. 5a shows a splint article having a soft region along the edge of the splint and around a thumb hole; Figs. 5b and 5c show the splint article of Fig. 5a fitted to a human arm and Fig. 5d shows a cover bandage wrapped around a human arm and over the splint article of Figs. 5b and 5c;

Fig. 6 shows a partially unwound roll of an extruded casting article with two soft areas along each edge of the casting tape;

Fig. 7a shows a test fixture used to support a ring of casting material when measuring edge strength; and

Fig. 7b shows a ring of hardened cast material located in the test fixture of Fig. 7a; and

Figures 8a-d show a slot die used to apply two or more resins to a substrate.

In Fig. 1, a partially unwound roll 10 of a casting tape 20 is shown in perspective view. The unwound portion of the casting tape 20 is shown with a central region 12, a first edge region 14 and a second edge region 16. The partially unwound web is shown with a first edge 15, a second edge 17 and a first end 13. A second end 19 is wrapped around the core of the roll and is not visible. At least one of the first edge region 14 and the second edge region 16 preferably have a hardness that is different from that of the central region 12. More preferably, at least one of the first edge region 14 and the second edge region 16 is a soft region and the central region 12 is a hard region. In a most preferred embodiment, both the first edge region 14 and the second edge area 16 soft areas, and the middle area 12 is a hard area.

In Fig. 2, a partially unwound roll 110 of a casting tape 120 is shown in perspective view. The unwound portion of the casting tape 120 is shown with a central region 112 and a first edge region 114. The partially unwound web is shown with a first edge 115, a second edge 117, and a first end 113. A second end 119 is wrapped around the core of the roll and is not visible. The first edge region 114 has a hardness that is different from that of the central region 112. In a preferred embodiment, the first edge region 114 is a soft region and the central region 112 is a hard region.

In Fig. 3, a partially unwound roll 210 of a casting tape 220 is shown in perspective view. The partially unwound web of casting tape 220 is shown with central regions 212, a first edge region 214, an optional second edge region 216, and an optional third region 218. The unwound portion is shown with a first edge 215, a second edge 217, and a first end 213. A second end 219 is wrapped around the core of the roll and is not visible. At least one of the first edge region 214, the second edge region 216, and the third region 218 has a hardness that is different from that of the central regions 212. In a preferred embodiment, the first edge region 214, the second edge region 216 and the third region 218 are each soft regions, and the middle regions 212 are hard regions.

Fig. 4 shows a human arm wrapped with a casting tape of the present invention. As shown in Fig. 4, the casting tape 20 has a central region 12 and at least one edge region 14 extending longitudinally of the tape. If desired, an optional second edge region 16 having a different hardness may also be used. When the casting tape 20 is used in a spiral pattern as shown in Part A, the edge regions 14, 16 overlap with the central region 12 of one or more adjacent wraps or layers. However, if desired, an edge region 14, 16 can overlap with an edge region 14, 16 of one or more adjacent wraps or layers. This can be accomplished, for example, at the casting edges 22, 24, 26 and 28. If desired, the casting tape of Fig. 4 can be advantageously used by folding the tape in half as it is wrapped around the thumb at 24. When so folded, a portion of the central region (shown as 218 in Fig. 3) becomes an edge of the double-layered tape and preferably results in a tape 220 having a soft region along each edge.

Fig. 5a shows a splint article 310 having a central hard region 312 and a soft region 314 along the perimeter of the splint article 310 and around a thumb hole 311. Figs. 5b and 5c show the splint article 310 of Fig. 5a fitted to a human arm. An optional padding material 330 is wrapped around or placed on the arm prior to applying the splint article 310. Fig. 5d shows a cover bandage 340 wrapped around the human arm and over the splint article 310 of Figs. 5b and 5c, thereby securing the splint article 310 to the arm.

Fig. 6 shows an extruded casting article or tape 420 having two soft regions. In Fig. 6a, a partially unwound roll 410 of casting tape 420 is shown in perspective view. The partially unwound extruded web of casting tape 420 is shown with a central region 412, a first edge region 414 and a second edge region 416. The unwound portion is shown with a first edge 415, a second edge 417 and a first end 413. A second end 419 is wrapped around the core of the roll and is not visible. At least one of the first edge region 414 and the second edge region 416 preferably has a hardness that differs from the of the central region 412. More preferably, at least one of the first edge region 414 and the second edge region 416 is a soft region, and the central region 412 is a hard region. In a most preferred embodiment, both the first edge region 414 and the second edge region 416 are soft regions, each comprising at least one extruded element of a soft casting material, and the central region 412 is a hard region comprising at least one extruded element, preferably a plurality of extruded elements, of a hard casting material.

Figure 7a shows a test fixture 700 used to support a ring of casting material 740 when measuring edge strength. The fixture includes a base 710, a bottom support 720 located at a 45º angle to the base 710, and a side support 724 located at a 90º angle to the bottom support 720. As shown in Figure 7b, a ring of casting material 740 is inserted into the test fixture 700 with a first end of the ring 741 resting on the bottom support 720. A portion of the side of the cylindrical ring of casting material 740 rests on the side support 724. The side support 724 includes a machined surface that matches the radius of the ring of casting material 740. A cylindrical probe 744 is pushed against the upper front edge 742 of the ring of casting material 740. The cylindrical probe 744 is attached to a testing apparatus 746, such as an Instron machine.

Fig. 8a shows a side view of a three-part slot die 800 used to apply two or more resins to a substrate. The die is shown with two outer plates 820a and 820b and a middle plate 810. As shown in Figs. 8b and 8c, the outer plates 820a and 820b include a plurality of screw holes 812. The outer plate 820a further includes feed holes 824, 826 and 828. The middle plate 810 includes a plurality of screw holes 812 and tapered flow cavities 814, 816 and 818 that communicate with the feed holes 824, 826 and 828, respectively. The tapered flow cavities direct the resin flow to obtain the coating widths E and C.

This invention employs certain principles and/or concepts as set forth in the claims appended to this specification. Those skilled in the casting art to which this invention pertains will appreciate that these principles and/or concepts may be embodied in a variety of embodiments that may differ from the precise embodiments used in this specification for purposes of explanation. For these reasons, the invention described in this specification should not be considered as limited to the illustrative embodiments only, but should be considered only in light of the appended claims.

Detailed description of the invention

The present invention provides a curable orthopedic support article having at least two regions of differing hardness. In a presently preferred embodiment, the support material comprises a flexible sheet material associated with (e.g., impregnated or coated) at least one liquid resin system that cures when exposed to a curing or activating agent. The support material preferably further comprises packaging means to prevent contact of the resin with the curing or activating agent prior to use. The invention also relates to a method of applying the support material and to the cured device formed from the support material. The invention further relates to a method of manufacturing the support material.

In an alternative embodiment, the support material comprises a flexible sheet material associated with (e.g., impregnated or coated) at least one thermoplastic material that changes from a first, moldable state to a second, dimensionally stable state upon cooling. In a further alternative embodiment, the support material comprises a extruded sheet material made of either a thermoplastic material or a viscous curable material.

Preferably, the orthopedic support article is in the form of an orthopedic casting tape comprising a fabric backing associated with two different curable resins. A harder first curable resin is associated with the central region of the fabric backing and a softer second curable resin is associated with at least one edge region of the fabric backing. More preferably, the casting tape comprises a central region of a conventional "hard" curable resin and two edge regions of a "soft" curable resin. When wrapped around a limb, the softer edge regions can overlap one another to form a soft, comfortable edge of the cured casting tape.

Alternatively, the orthopedic support material may be in the form of a casting tape comprising a single resin impregnated or coated onto a fabric backing. In this embodiment, the fabric backing itself comprises at least two different materials or two different constructions of the same type of material. For example, the fabric may be knitted using two different types of yarns. A first type of yarn (e.g., fiberglass) may be used to form a central region of the fabric, while a second, softer type of yarn (e.g., polyester, cotton, rayon, polyolefin, polyurethane, etc.) may be used to form at least an edge region of the fabric. The softer edge yarns provide a hardened fabric with a lower modulus of elasticity compared to the fiberglass yarns in the center, which have a higher modulus of elasticity. The fabric may alternatively be knitted using a single type of yarn, but in such a way that a first region of the fabric absorbs more or less of the hardenable resin. For example, the ability of a long-row yarn to absorb resin can be adjusted by increasing or decreasing the number of fibers in the long-row yarn. In this way, more or less resin can be supplied to a particular row, resulting in different hardness of the cured resin-impregnated fabric.

If desired, a combination of these techniques can also be used. For example, the orthopaedic support material can be in the form of a casting tape comprising two different resins impregnated or coated onto a fabric carrier comprising two different materials.

As previously mentioned, one or more curable resins may be associated with the backing. In a presently preferred embodiment, the casting tape comprises two different curable resin formulations. A harder first curable resin formulation is used to coat the central region of the casting tape, and a softer second curable resin formulation is used to coat at least an edge region of the casting tape. The first and second resin formulations may be similar, e.g., from the same chemical class, and differ only in their respective physical properties when cured (e.g., both resins may be water-curable isocyanate-functional resins). Alternatively, the first and second resin formulations may be from different chemical classes. Preferably, the two resins are compatible with each other and bond well together, e.g., from the same chemical class. B. when adjacent layers of the casting tape overlap each other and cause contact of the two resin formulations. Most preferably the two resins comprise the same base chemistry.

The curable resin used in the hard portion of the casting material is preferably any curable resin that meets the functional requirements of an orthopaedic casting. Of course, the resin must be non-toxic (i.e., it must not emit significant amounts of toxic fumes when cured that may be harmful to either the patient or the person applying the casting) and must not cause skin irritation (e.g. either through chemical irritation or through generation of excessive heat during curing). Furthermore, the resin must be sufficiently reactive to the curing agent to ensure rapid curing of the cast once it is applied, but not so reactive that it does not allow sufficient working time to apply and shape the cast. Initially, the cast material must be pliable and malleable and should adhere to itself. Then, in a short time after completion of cast application, it should become sufficiently stiff and sufficiently strong to withstand stresses and strains to which the cast is subjected by the activities of the wearer.

The following disclosure relates primarily to the presently preferred embodiments of the invention, wherein water-curable isocyanate-functional prepolymers are used as the curable resin. Other suitable curable resins are discussed later.

Some currently particularly preferred hard resins for use in the present invention are water-curable isocyanate-functional prepolymers. Suitable systems of this type are disclosed, for example, in U.S. Patent Nos. 4,131,114, 4,376,438, 4,433,680, 4,411,262, 4,433,680, and 4,502,479. Currently particularly preferred resin systems are disclosed in U.S. Patent No. 4,667,661 and U.S. Patent Application Serial Nos. 07/376,421 and 08/320,917.

As used herein, the term "water-curable isocyanate-functional prepolymer" means a prepolymer derived from a polyisocyanate compound and a compound or oligomer containing reactive hydrogen (e.g., a "polyol"). A compound containing reactive hydrogen is a compound containing active hydrogen in accordance with the well-known Zerevitinov test, as described, for example, in Chemistry of Organic Compounds by Carl R. Noller, Chapter 6, pp. 121-122 (1957). The prepolymer has sufficient isocyanate functionality to cure upon exposure to water, e.g., water vapor or, preferably, liquid water.

Currently, a polyisocyanate prepolymer is preferably used, which is formed by the reaction of an isocyanate and a polyol.

Suitable isocyanates are disclosed, for example, in U.S. Patent Nos. 4,376,438, 4,433,680, and 4,502,479 and include: 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, and mixtures of these isomers, 4,4'-diphenylmethane diisocyanate, 2,4'-diphenylmethane diisocyanate, and possible mixtures of these isomers with small amounts of 2,2'-diphenylmethane diisocyanate (typical of commercially available diphenylmethane diisocyanate), and aromatic polyisocyanates and their mixtures such as those derived from the phosgenation of the condensation product of aniline and formaldehyde. Preferably, a low volatility isocyanate such as diphenylmethane diisocyanate (MDI) is used rather than a more volatile material such as toluene diisocyanate (TDI). Suitable commercially available isocyanate precursors include "ISONATE" 2143L (available from Dow Chemical Co.), "MONDUR" MRS (Mobay Chem. Co., Pittsburgh, PA), and "PAPI" (Dow Chemical Co.).

Suitable polyols for use in the prepolymer system include polyalkylene oxides (e.g., polyethylene oxide and polybutylene oxide), polypropylene ether glycols (available from Arco Chemical under the trade name "Arcol PPG" and from BASF Wyandotte under the trade name "Pluracol"), polytetramethylene ether glycols (e.g., "Polymeg" from Quaker Oats Co. or "Terathane" from E. I. Du Pont de Nemours Co., Wilmington, DE), polycaprolactone diols (e.g., "Tone" series of polyols from Union Carbide), and polyester polyols (e.g., hydroxy-terminated polyesters obtained by esterification of dicarboxylic acids and diols; such as the "Rucoflex" polyols available from the Ruco Division, Hooker Chemical Co.). By using low molecular weight polyols, the stiffness of the cured resin can generally be increased.

An example of a "hard resin" suitable for the casting material of the invention uses an isocyanate known as IsonateTM 2143L available from Dow Chemical Company (a mixture of di- and triisocyanates containing about 73% MDI) and a polypropylene oxide polyol which available from Arco Chemical and known as Arcol PPG725. To increase the storage stability of the material, it preferably contains 0.01 to 1.0% by weight of benzoyl chloride or other suitable stabilizer (based on the total weight of the resin).

To form a currently preferred hard resin, the isocyanates and the polyols are reacted under conventional polyurethane reaction conditions known to those skilled in the art. The NCO:OH ratio of the reactants is preferably between 1.5:1 and 7:1 and more preferably between 2.5:1 and 4.5:1.

In general, the hardness of a resin can be influenced by adjusting the "functionality" of the reactants. As functionality increases, e.g. as the relative amount of polyfunctional material compared to difunctional material increases, the hardness increases. In addition, the hardness of a resin can generally be influenced by adjusting the "equivalent weight" of the reactants for a given NCO:OH ratio. As the equivalent weight increases, e.g. as the equivalent weight of the polyol increases, the hardness decreases.

To form a presently preferred rigid resin having an NCO:OH ratio in the range of 2.5:1 to 4.5:1, the theoretical isocyanate equivalent weight of the prepolymer (grams resin/equivalent isocyanate) is preferably less than about 1000 grams, more preferably less than about 500 grams, and most preferably less than about 400 grams. Preferably, the theoretical polyol equivalent weight of the prepolymer is less than about 1000 grams, more preferably less than about 500 grams, and most preferably less than about 400 grams. Of course, these weights could have different values if the resin were to contain an adjuvant such as a plasticizer or utilize a different NCO:OH ratio or average functionality of the reactants.

One or more areas of the cast tape, e.g. one or both edge areas, are preferably coated with a "soft resin". Some Presently particularly preferred soft resins for use in the present invention are water-curable isocyanate-functional prepolymers, such as those disclosed in U.S. Patent No. 4,968,542.

Suitable and presently most preferred soft resins for use in the support materials of the present invention include moisture-curing polyurethane prepolymers prepared by reacting a polyol with an excess of polyisocyanate. The starting materials can be from the same classes of chemicals used to form the rigid (or "hard") polyurethane casting materials well known in the art, such as those described in U.S. Patent Nos. 4,376,438, 4,433,680, 4,502,479 and 4,667,661. The isocyanate equivalent weights of the prepolymers, the NCO:OH ratio and/or the average hydroxy equivalent weight of the polyol are modified to provide the semi-rigid properties of the soft region.

In addition, other active hydrogen materials can be used alone or in combination with polyols to make soft resins suitable for this invention. Examples include primary and secondary amines, carboxylic acids, and thiols. When materials such as these are used, the total equivalent weight of the active hydrogen components should preferably be at least 400 grams, and most preferably at least 1000 grams.

Suitable isocyanates include those disclosed above. Preferred include 2,4'-diphenylmethane diisocyanate, 4,4'- diphenylmethane diisocyanate, and possible mixtures of these isomers with small amounts of 2,2'-diphenylmethane diisocyanate (typical of commercially available diphenylmethane diisocyanate). Suitable commercially available isocyanate precursors include "ISONATE" 2143L (Dow Chemical Co.); "MONDUR" MRS (Mobay Chem. Co., Pittsburg, PA) and "PAPI" (Dow Chemical Co.).

The degree of stiffness and elasticity in the cured support is generally influenced by the average hydroxy equivalent weight of the polyol or polyol blend. The choice of hydroxy equivalent weight also depends on the molecular structure and type of isocyanate, as is well known.

Suitable polyols for use in the prepolymer resin system include polyalkylene ethers derived from the condensation of alkylene oxides (such as those available from Arco Chemical under the trade name "Arcol PPG" and from BASF Wyandotte under the trade name "Pluracol"), polytetramethylene ether glycols (such as "Polymeg" from Quaker Oats Co.), polycaprolactone polyols, and polyester polyols (hydroxy-terminated polyesters obtained by esterification of dicarboxylic acids and diols) such as the "Rucoflex" polyols available from Ruco Division, Hooker Chemical Co. By using higher molecular weight polyols, the stiffness of the cured resin can generally be reduced.

A particularly preferred resin for use in the edge region of the support materials of the invention employs an isocyanate known as "Isonate" 2143L available from Dow Chemical (a mixture of isocyanate compounds containing about 73% by weight diphenylmethane diisocyanate) and a mixture of polypropylene oxide polyols available from Arco Chemical as Arcol LHT-28 and PPG 425. To increase the shelf life of the material, it preferably contains about 0.02 to 0.1% by weight benzoyl chloride and/or another suitable stabilizer (e.g., an antioxidant such as butylated hydroxytoluene in an amount of about 0.05 to 0.25% by weight).

The isocyanates and the polyols are reacted under conventional polyurethane reaction conditions known to those skilled in the art. The NCO:OH ratio of the reactants is in the range of about 1.5:1 to 7:1 and preferably between 2.5:1 and 4.5:1.

In general, the softness of a resin can be influenced by adjusting the "functionality" of the reactants. As functionality increases, e.g. because the relative amount of polyfunctional material compared to difunctional material increases, the softness decreases. However, the elasticity of the material may increase somewhat. In addition, the softness of a resin can generally be influenced by adjusting the "equivalent weight" of the reactants for a given NCO:OH ratio. As the equivalent weight increases, e.g. because the equivalent weight of the polyol is increased, the softness increases.

To form a presently preferred soft resin having an NCO:OH ratio between 2.5:1 and 4.5:1, the theoretical isocyanate equivalent weight of the prepolymer is preferably greater than about 400 grams, more preferably greater than about 500 grams, and most preferably greater than about 1000 grams. Preferably, the theoretical polyol equivalent weight of the prepolymer is greater than about 400 grams, more preferably greater than about 500 grams, and most preferably greater than about 1000 grams. Of course, these weights could have different values if the resin were to contain an adjuvant such as a plasticizer (which generally reduces the stiffness of the cured resin), or utilize a different NCO:OH ratio or average functionality of the reactants.

The reactivity of the one or more resins once exposed to the water curing agent can be controlled by the use of an appropriate amount of a suitable catalyst. The reactivity must not be so great that (1) a hard film quickly forms on the resin surface preventing further penetration of the water into the bulk of the resin or (2) the dressing becomes stiff before application and molding is complete. Good results have been obtained using 4-[2-[1-methyl-2-(4-morpholinyl)ethoxy]ethyl]morpholine ("MEMPE") prepared as described in U.S. Patent No. 4,705,840 and 2,2'-dimorpholinodiethyl ether ("DMDEE") prepared as described in U.S. Patent No. 4,433,680 at a concentration from about 0.05 to about 5 weight percent (based on the total weight of the resin). To prepare the cured supports of the present invention, a cure time of about 2.5 to 18 minutes after exposure to the curing agent, e.g., after immersion in water, is preferred. More preferably, the cure time is between about 3 and 10 minutes, and most preferably between about 3 and 5 minutes.

In general, foaming of the resin in the hard portion of the casting tape should be minimized because it can affect the surface smoothness of the casting tape and reduce its overall strength. For example, foaming can occur when carbon dioxide is released as a result of water reacting with an isocyanate group. One way to minimize foaming is to reduce the concentration of isocyanate groups in the prepolymer. However, to maintain reactivity, processability, and fracture toughness, a sufficient concentration of isocyanate groups is necessary. Although foaming is reduced at low resin contents (e.g., low resin coating weights), a sufficient resin content is required to achieve the desired properties of the casting tape, such as strength and peel strength. A satisfactory method of minimizing foaming is to add a foam suppressor such as Antifoam A silicone (Dow Corning) or Anti-Foam 1400 silicone fluid (Dow Corning) to the resin. It is particularly preferred to use a silicone fluid such as Anti-Foam 1400 from Dow Corning at a concentration of about 0.05 to 1.0% by weight. Water-curable resins containing a stable dispersion of hydrophobic polymeric particles such as disclosed in European Patent Publication EP 0 407 056 may also be used to reduce foaming.

If desired, foaming of the resin in the soft area of the casting tape can be used to advantage. For example, foaming can have the desired effect of reducing the stiffness of the edge area of the casting tape. Foaming can by coating at least one edge region of the tape with a resin that does not contain an antifoaming agent (thereby allowing natural foaming during curing of the resin) or by coating the region with a resin that contains a foaming agent such as Union Carbide's GR-5M Triton surfactant.

Preferably, lubricants are added to the resin or resins, as described, for example, in U.S. Patent Nos. 4,667,661 and 4,794,937, so that the casting materials exhibit reduced tack before and during cure, yet still form a casting with acceptable strength and peel strength. This is especially true for the soft resins used in the peripheral region. These resins are often even tackier than those used to form castings. Suitable lubricants include: hydrophilic groups covalently bonded to the resin system; additives incompatible with the curable resin, including surfactants, polymers comprising multiple hydrophilic groups, and polysiloxanes, and combinations of the above. The lubricant may, if desired, be used in conjunction with a separate volatile liner as disclosed in U.S. Patent Application No. 08/404,242.

The preferred method for reducing the tackiness of the polyurethane prepolymer resin systems involves the addition of a lubricant, particularly a surfactant, to the system. The preferred surfactants are block copolymers of propylene oxide and ethylene oxide or polyethylene oxides which are solid at 23°C, in an amount ranging from 3 to 6% by weight of the prepolymer system. Particularly preferred are hydroxy-functional polyethylene oxide-terminated polypropylene oxides (sold by BASF Wyandotte under the trade name "Pluronic").

Plasticizers may be added to the resin to adjust the hardness of the cured resin. Suitable plasticizers are well known in the art and are preferably added to the soft resin in such amounts given that the cured article has the desired level of softness. Preferably, the plasticizer does not affect the storage stability of the uncured casting tape or otherwise affect the physical or toxicological properties of the material. Suitable plasticizers include materials such as butylbenzene phthalate, Sanicizer 160, from Monsanto Chemical Co.

Currently preferred resins are the above-mentioned urethane resins, which are formed by the reaction of a polyisocyanate and a polyol. Other water-curable resins known in the art (optionally combined with moisture-sensitive catalysts) may be suitable; these include polyurethanes, cyanoacrylic acid esters, epoxy resins and prepolymers terminated at their ends with trialkoxy or trihalosilane groups.

Resin systems other than water-curable may be used, although the use of water to activate the cure of an orthopedic casting tape is the most convenient, safe and familiar to orthopedic surgeons and medical personnel applying castings. Preferred resins are not appreciably dispersible in water. Suitable water-activated and alternative curing resins include moisture-curable polyurea prepolymers, silane, siloxane, epoxy, acrylate, polysulfide and polyester functional materials. Light-curable materials such as certain active olefins, e.g. acrylates and compounds with pendant vinyl groups are also candidates.

Suitable resins include those disclosed in U.S. Patent No. 3,908,644, in which a tape is impregnated with difunctional acrylates or methacrylates, such as bis(methacrylic acid ester) derived from the condensation of glycidyl methacrylate and bisphenol A (4,4'-isopropylidenediphenol). The resin can be cured upon wetting with solutions of a tertiary amine and an organic peroxide. Alternatively, U.S. Patent No. 3,630,194 proposes an orthopedic tape impregnated with acrylamide monomers, the polymerization of which is induced by immersing the tape in a aqueous solution of oxidizing and reducing agents (known in the art as redox initiator system).

Also suitable as resins in this invention are water-curable alkoxysilane-terminated oligomers as disclosed in U.S. Patent No. 5,423,735.

Also suitable as resins in this invention are water-reactive liquid organometallic compounds as disclosed in pending U.S. Patent Application Serial Nos. 08/008,678 and 08/008,743. These resins generally consist of a water-reactive liquid organometallic compound and an organic polymer.

It is desirable that the rheology of the curable resin be adjusted so that the resin is easily applied to the backing at the desired coating weight, but does not "run together" during storage. When two different resins are used, it is particularly preferred that the different resins resist undesirable migration, which would affect the unique physical properties of the different regions of the casting tape when cured. This can be accomplished, for example, by providing one or more of the resins in a form that resists migration.

The flexible sheet material used in the support material of the present invention is preferably porous so that the sheet is at least partially impregnated with the resin. A porous sheet material also facilitates the circulation of air through the cured device and the evaporation of moisture from beneath the device. This contributes to patient comfort and the maintenance of healthy skin beneath the device.

Examples of suitable flexible web materials are woven or knitted textile fabrics made of natural or synthetic fibers such as polyamide, polyester, cotton, rayon, polyolefin, etc. Preferred Web materials are stretchable knits of fiberglass or polyester. Suitable fiberglass fabrics are disclosed in U.S. Patent Nos. 4,502,479, 4,609,578, 4,668,563, and 5,014,403 and in U.S. Patent Application Serial Nos. 07/976,402 and 08/008,751. Particularly preferred webs of this type are stretchable, heat-settable fabrics such as those disclosed in U.S. Patent No. 4,609,578 (Reed).

Preferred web materials used in the backing material are generally long, narrow strips of fabric (tapes) wound into rolls of varying widths, e.g., about 5 cm to about 15 cm wide. The fabric is impregnated with the curable resin material in an amount of about 30 to 90% by weight of the backing material, and in the preferred embodiment employing a fiberglass fabric, in an amount of 40 to 60% by weight of the impregnated backing material. The term "impregnation" is used to describe the state in which the resin is thoroughly mixed with and surrounds the threads or fibers of the fabric, and does not necessarily indicate that the resin is absorbed by the fibers themselves at all. Generally, the resin solution flows into the capillary spaces between adjacent filaments of the fabric and, upon curing, becomes bonded to the fabric.

The amount of resin component applied to the fabric must be sufficient to form a laminate bond between the layers, but preferably not so large that the pores become clogged. Excess resin component may also make the support material difficult to handle due to stickiness or dripping of the resin.

If desired, the fabric may be knitted using two different types of long-row yarns. A first type of yarn (e.g., fiberglass) may be used to form a central region of the fabric, while a second, softer type of yarn (e.g., polyester) may be used to form at least an edge region of the fabric. The softer Edge yarns provide a hardened edge region with a lower modulus of elasticity compared to the central region which has a higher modulus of elasticity. The fabric may alternatively be knitted using a single type of yarn or treated in such a way that a first region of the fabric absorbs more or less of the hardenable resin. For example, the capacity of a long row yarn to absorb resin may be adjusted by increasing or decreasing the number of fibers in the long row yarn. In this way, more or less resin may be directed to a particular long row, resulting in a different hardness of the hardened fabric.

The resin-coated fabric strips in roll form are preferably wound on a plastic core and sealed within a moisture and oxygen impermeable package. In the case of moisture-curing resins, the package is only opened immediately before use and the roll is completely immersed in tap water for approximately 5 to 30 seconds. This is sufficient time for water to slowly penetrate the porous material and displace air. As long as the resin content is not so high that the openings in the fabric are filled with resin, more than enough water will be absorbed by the roll in this way. The roll can be squeezed underwater to replace trapped air with water. As the roll is unwound while the material is being wrapped around the limb, the excess moisture coats freshly exposed resin surfaces, ensuring thorough wetting and rapid curing of the material. An alternative method involves wrapping the material without immersion and then allowing the prepolymer to cure by air humidity or water provided by spraying or by applying a damp towel.

Before applying the support material, a protective pad is placed around the patient's limb if necessary. The pad may be in the form of a tubular stockinette or any other suitable shape such as the form of an elongated strip or band that can be wrapped around the limb.

Once the pad is in position, the moistened support material is wrapped around the limb and over the protective pad in a manner similar to that used to apply a standard cast material. The material is also shaped in a manner similar to that used to shape a rigid synthetic or plaster cast. When wrapped in a spiral pattern as shown in part A of Figure 4, the edge regions overlap the central region of one or more adjacent layers. Consequently, the strength of the cast in this region is not significantly compromised. Preferably, however, the edge region near the edge of the cast overlaps the edge region of one or more adjacent layers, creating a soft edge of the hardened cast.

Eight or fewer layers of support material should generally be sufficient to form a cured device that provides adequate support and/or immobilization for most applications.

The cured casts of the present invention are characterized by their flexible and resilient edges as compared to conventional casts formed from synthetic resins.

In an alternative embodiment, the support material comprises an extruded sheet material of either a thermoplastic material or a viscous curable material. Suitable extruded sheet materials are disclosed in copending U.S. Patent Application Nos. 08/048,891, 08/391,111, 08/391,712 and 08/449,505. According to the present invention, the extruded sheet is formed using at least two strips of extruded material having different properties in the cured state.

The extrusion process can produce a product with any number of configurations, including random shapes such as found in Nomad matting (available from 3M and described in U.S. Patent No. 4,351,683). Alternatively, the apertured web can be extruded as a continuous, non-apertured web which is then punched or drilled to form an apertured web. Currently preferred extruded apertured webs are formed by the "Z-Web" process disclosed in U.S. Patent Nos. 4,631,215 and 4,634,485 or by the "spiral" process disclosed in U.S. Patent No. 4,384,022. Another suitable process, the "conwed" process, results in an extruded network with two groups of strands that cross each other substantially at right angles and that may be molecularly oriented (for example, described in U.S. Patent Nos. 2,919,467, 3,252,181 and 4,152,479).

The Z-Web process is currently the most preferred because it is capable of producing a wide variety of webs with varying density of apertures and variing thickness, and because construction and maintenance are relatively easy. The Z-Web process operates primarily due to different pressure drops across the apertures in the die face, resulting in different mass flow rates of the extrudate, thus creating the "zigzag" or Z-Web pattern. A typical web pattern is shown in Fig. 6. Articles formed by the Z-Web process are manufactured using the following procedures:

(1) extruding a first filament-forming extrudable plastic mass at a first rate to form a plurality of straight, spaced, parallel elements;

(2) extruding a second filament-forming extrudable plastic mass (at a second speed greater than the first extrusion speed, between adjacent spaced endless parallel elements) which is preferably thinner than wide, such that a cross-section having an aspect ratio of preferably at least about two is obtained, the undulatable element being positioned so that each of the opposing surfaces of its wide dimension faces one of the straight endless parallel elements, and the plastics masses having a sticky first state which enables the elements to bond together at points of contact and a second physical state in which the elements have sufficient structural integrity to maintain their shape in the extruded and bonded state, in which latter state there is preferably no longer any sticking which would lead to deformation of the web and closure of the openings;

(3) causing the undulatable element to undulate in its thin direction while the elements are sufficiently tacky to cause bonding between them at points of contact by allowing contact between a parallel element on one side of the undulatable element while keeping the other, adjacent parallel element sufficiently close to allow subsequent contact between it and the undulating undulatable element and to allow repetition of the undulation and subsequent contact, thereby obtaining an article having an undulated element with vertices on opposite sides aligned in a line, the vertices on one side of the undulated element being bonded to one of the parallel elements and the vertices on the other side of the undulated element being bonded to the other, adjacent parallel element; and

(4) Converting or allowing the plastic masses to pass into the second physical state.

Webs made using the Z-Web process can aesthetically resemble a knitted fabric. To ensure adequate breathability in the tape form, webs made using the Z-Web process preferably have between 7.75 and 77.50 apertures per cm², more preferably between 15.50 and 62.00 apertures per cm², and most preferably between 23.25 and 38.75 apertures per cm². A cast that has sufficient porosity to allow water vapor generated by the skin to freely escape through the cast is referred to herein as "breathable" or "breathable." For the Z-Web configuration, an aperture is defined as an aperture of the triangular or sinusoidal type as shown in Figure 6. Preferred Z-Web casting tapes are as breathable as typical fiberglass casting tapes such as Scotchcast Plus (available from 3M Co., St. Paul, MN). Water vapor transmission and air flow through a casting material can be tested as described in the above-referenced patent applications. Preferably, the casting tapes of the present invention have air flow and water vapor transmission comparable to those of plaster of Paris or conventional fiberglass casting materials.

The spiral process is also preferred because it is capable of producing a wide variety of webs with varying density of "apertures" and varying thickness, and because construction and maintenance are relatively easy. The spiral process also operates primarily due to different pressure drops across the orifices in the die face, resulting in different mass flow rates of the extrudate, thereby creating the spiral pattern. Unlike the Z-Web process, the spiral process uses a die that includes one or more inner orifices and multiple outer orifices (at least three) surrounding each inner orifice. The geometry of the die produces a web that includes one or more filament bundles having a spiral inner extrudate surrounded by a plurality of straight, parallel outer "cage" filaments. The sizes and cross-sectional shapes of the orifices determine the size and shape of the filaments extruded through. For a given distance between the inner opening and the outer openings, the pitch of the spiral core filament is determined by the relative flow of material through the inner and outer holes. That is, the pitch decreases as the speed difference increases.

The "Nomad" process is described in U.S. Patent No. 4,351,683. This process is capable of forming an elastic open-fiber web of interlocking, continuous, kinked filaments. The process involves extruding a bundle of filaments from a material having a sticky first state that allows the elements to bond together at points of contact and a second physical state in which the elements have sufficient structural integrity to maintain their shape in the extruded and bonded state, in which latter state bonding preferably no longer occurs, orienting the bundles so that the filaments fall onto a contact surface, and advancing the resulting web at a speed less than the extrusion speed.

Webs made by the spiral or "Nomad" process should preferably have a sufficient number of "openings" to provide adequate breathability, preferably as great a breathability as the Z-Web materials. However, due to the geometry of the spiral webs and the statistical nature of the Nomad webs, it is difficult to specifically count the number of openings per unit area. An alternative method of quantifying the breathability of these webs is to calculate the open volume of the web. Suitable webs made by the spiral or Nomad process have a sufficient percentage open volume to provide adequate breathability. Particularly preferred webs have as great a breathability as the Z-Web materials or typical fiberglass casting tapes such as 3M's Scotchcast Plus. The "open volume" of a web, as the term is used herein, is determined by first weighing a known volume of the web to determine the density of the web. Then the volume of extrudate in that area of the web is calculated by dividing the measured weight of the web by the density of the extrudate. The volume of extrudate divided by the volume of the web, calculated as the area of the web times its average thickness, gives the fraction of extrudate in the mat which, when subtracted from one and multiplied by 100, gives the percent open volume. The thickness of the web is determined using an Ames Model 2 thickness gauge (Waltham, MA).

To ensure good conformability, formability and handleability, and yet provide sufficient strength, the thickness of the tape should be between 0.25 and 8.0 mm, preferably between 0.5 and 4.0 mm, and most preferably between 0.75 and 2.00 mm. An orthopedic splint can be formed from several layers of thinner tape, or it can be directly extruded in thicker form. If directly extruded, the material could have 1.55 to 46.5 openings per cm2 (or equivalent opening volume) and have a thickness between 2.54 and 12.70 mm, preferably between 5.08 and 8.89 mm.

In one embodiment of the present invention, an extruded casting tape or splint is provided as a thermoplastic apertured web. This embodiment provides an environmentally friendly and safe alternative in the manufacture of casting tapes. The thermoplastic casting tape preferably comprises an extruded apertured web comprising at least two different strips of thermoplastic polymers with controlled rheology of the amorphous phase. A first polymer composition forms a soft casting material when cooled to room temperature, the second polymer composition forms a hard casting material when cooled to room temperature. Preferably, the soft casting material forms at least one edge of the casting tape.

Suitable thermoplastic polymers for use in the present invention are those polymers that soften or melt at temperatures that the patient and/or professional can comfortably tolerate when applying the casting. This temperature is likely to be less than about 90°C, preferably less than about 75°C, although somewhat higher temperatures may be acceptable (particularly in situations where direct contact between the casting material and the skin is avoided). Suitable thermoplastic polymers include polyurethanes (particularly polyurethanes based on semi-crystalline polyester polyols), polyethylene, ethylene vinyl acetate, cis- and trans-polyisoprene, polyesters such as polycaprolactone, and the like. The presently preferred thermoplastic polymers for use in the present invention are semi-crystalline polyesters. Polycaprolactone and blends of polycaprolactone are particularly preferred.

In a second embodiment of the present invention, an extruded casting tape or splint is provided as an apertured sheet coated with a viscous curable resin. This embodiment provides a product that has very good conformability and should be inexpensive to manufacture. Casting materials of this embodiment preferably do not require expensive disposable release liners or fabric backings and provide a moldable slippery material that is easy to apply.

The casting tape comprising the viscous curable resin preferably comprises an extruded apertured web comprising a curable, preferably water-curable, resin having sufficient viscosity or yield stress to not flow for extended periods at room temperature. The casting tape comprising an extruded viscous curable resin preferably contains no carrier (or only a light carrier). Therefore, the conformability and handleability of the tape is primarily determined by the viscosity of the curable resin component. By adjusting the rheological properties of the resin, a product with superior adaptability and moldability, and is also much cheaper to produce than current synthetic casting tapes.

Curing of the resin can be initiated by exposure to water or by a conventional free radical mechanism. Water-curable resins are preferred because they are most convenient and familiar to the clinician. Therefore, while the following discussion focuses on water-curable resins, it should be understood that materials cured by other means are also suitable.

A key technical feature of the present invention is the development of a curable, preferably water-curable, resin system that can be extruded through a suitable die and then subsequently gelled to a viscous or high yield stress state. As used herein, the terms "gelling" or "gelled" describe materials that have or develop a sufficiently high yield stress to not flow for extended periods at room temperature. Preferred materials are gelled to a point where the integrity of the web is sufficient to withstand a stress of at least 0.0175 N/mm width, more preferably at least 0.0875 N/mm width, and most preferably above 0.175 N/mm width without tearing and without collapsing a substantial portion of the extruded apertures or voids. Preferred materials have a storage or elastic modulus G' of at least 0.1 dyne/cm² at 0.1 rad/s and 1 dyne/cm² at 1.0 rad/s. Most preferably, G' is at least 1 dyne/cm² at 0.1 rad/s and 10 dyne/cm² at 1.0 rad/s, as determined using a parallel plate rheometer such as a Rheometrics Dynamic Analyzer Model RDA-II. For room temperature curable resins, G' is determined at 25°C under an inert atmosphere. For thermoplastic resins, G' is determined at 5 degrees above the melting temperature used in applying the casting material.

A "gelled" resin system can be achieved by forming a composite of inorganic and organic fillers and a resin. Suitable Concentrations of filler in the resin (i.e., the "filler loading") vary depending on the bulk density of the filler, the specific gravity of the filler, and the particular resin employed. An appropriate filler loading is determined by choosing an amount that is sufficiently large to provide adequate composite strength and good web integrity, but not so large that the composite easily breaks or crumbles or is difficult to extrude. Preferably, the filler loading is also large enough that the clinician can apply the material to the patient's limb without the need for gloves.

The curable resin used in the casting material of this embodiment of the present invention is preferably any curable resin that meets the functional requirements of an orthopedic casting. Of course, the resin must be nontoxic in the sense that when cured it does not emit significant amounts of toxic fumes that may be harmful to either the patient or the person applying the casting, and also that it does not cause skin irritation either by chemical irritation or by generating excessive heat during curing. Furthermore, the resin must be sufficiently reactive to the curing agent to ensure rapid curing of the casting once it is applied, but not so reactive that it does not allow sufficient working time to apply and shape the casting. Initially, the casting material must be pliable and moldable and should adhere to itself. Then, within a short time after the dressing application is complete, it should become rigid and strong enough to withstand the stresses and strains to which the dressing is subjected by the wearer's activities. In the case of the soft area, it should become at least semi-rigid. The material must therefore undergo a change of state from a viscoelastic state (e.g. a material with a sufficiently high yield stress so that it does not flow for a long time at room temperature) to a solid state within minutes. The preferred resins are those that are cured with water. Currently Preferred are urethane resins cured by the reaction of a polyisocyanate and a polyol as described herein.

The materials and compositions of the present invention can be fabricated into a variety of configurations including splints, bands and preformed parts.

As previously mentioned, the preferred web materials used in the support material are generally long, narrow strips of fabric (tapes) formed into rolls of various widths, e.g., about 5 cm to about 15 cm wide. Likewise, the support devices are generally long, narrow tapes formed into rolls of various widths. Suitable cured support articles have a central region and at least one edge region of varying hardness. Preferred cured support articles have two soft edge regions.

For use as an orthopedic cast, the edge region is preferably wide enough so that the cured cast provides a "soft" edge that does not abrade or cut the wearer's skin or otherwise injure the wearer. For a typical 10 cm wide cast, the edge region is preferably at least 0.5 cm wide, more preferably at least 1 cm wide, and most preferably at least 1.5 cm wide. The edge region is preferably narrow enough so that the cured cast provides a rigid support device that can support the weight normally borne by the limb around which the support device is wrapped. For a typical 10 cm wide cast, the edge region is preferably less than 4 cm wide, more preferably less than 3 cm wide, and most preferably less than 2 cm wide.

Typical commercially available synthetic orthopedic casting materials comprise a knitted glass fiber fabric impregnated with a polyisocyanate prepolymer resin. Typical glass fiber fabrics comprise between about 4 and 7 long rows per cm width. Consequently, a For example, a 10 cm wide casting tape will typically comprise between about 40 and 70 rovings. For a 10 cm wide fiberglass casting tape, the edge region preferably comprises at least 2 rovings, more preferably at least 5 rovings, and most preferably at least 7 rovings. In addition, for such a casting tape, the edge region preferably comprises less than 20 rovings, more preferably less than 15 rovings, and most preferably less than 10 rovings. "Comprising" in reference to the rovings means that the rovings are coated with a special resin that provides a soft region, or that the rovings are formed using a special yarn that provides a soft region, or by a combination of both mechanisms.

The present invention relates to an article suitable for forming an orthopedic splint around a portion of an animal's body part. When fabricated as a splint, the material may be provided as a pre-cut sheet (as shown, for example, in Figures 5a-d) or in continuous form. The soft edge region may extend along the long side of the splint or be located at the ends or both. For example, a rectangular splint material preferably includes a soft edge around all four edges of the splint and near any holes for extensions, e.g., thumb holes. Furthermore, the splint may be provided with or without a cover and/or padding. Suitable covers and padding for use in this invention are discussed in U.S. Patent Nos. 5,027,803 and 4,899,738. The splint may have a padding material on one or both sides.

According to a presently preferred embodiment of the invention, a unitary blank is provided comprising a flexible, preferably stretchable, and highly conformable substrate. The blank is sufficiently dimensioned in a first direction to extend the length of the body part and is sufficiently dimensioned in a second direction to partially, but preferably not completely, extend around the circumference of the body part. In this regard, the blank is dimensioned in the second direction to wrap the body part as far as necessary to support and immobilize the body part while still allowing room for the swelling that generally occurs as a result of a recent fracture or soft tissue injury.

The blank preferably comprises a carrier and a water-curable isocyanate-functional prepolymer resin with which the carrier is impregnated.

Fig. 5a is a top view of a preferred forearm embodiment of the orthopedic splint of the present invention prior to application; Fig. 5b is a perspective view of one side of the orthopedic splint of Fig. 5a that has been trimmed and formed into a forearm splint; Fig. 5c is a perspective view of the opposite side of the orthopedic splint shown in Fig. 5b; and Fig. 5d is a perspective view of the embodiment of Fig. 5b additionally showing a bandage that can optionally be wrapped around the splint to provide better conformability and attachment of the splint to the forearm.

Referring now to Figure 5a, there is shown a top view of a preferred orthopedic forearm splint article 310 of the present invention in the form of a unitary blank. The article or blank 310 is generally made of a flexible sheet and preferably has a thumb hole 311 formed therein to facilitate fitting the article 310 around the forearm of a wearer as shown in Figures 5b-d. Article 310 of Figure 5a may initially be configured as a rectangle and then trimmed to fit the patient as shown in Figures 5b and 5c. In this regard, the physical properties of the sheet material preferably allow for easy trimming.

The sheet of Article 310 preferably comprises a suitable backing material and a curable resin associated with the backing. Suitable backing materials include knitted, woven or nonwoven textile materials, sheets of open cell foam, and the like.

For the forearm splint embodiment of Figures 5a-d, a plate that is approximately 7 inches wide, 12 inches long, and 1/2 inch thick is currently preferred. For the lower leg embodiment, a foam plate that is approximately 10 inches wide, 38 inches long, and 1/2 inch thick is currently preferred. It will be appreciated, however, that the exact dimensions employed may vary in accordance with the particular limb size of the individual being treated.

The orthopedic splint article 310 is sized to fit the patient's forearm and may be trimmed prior to application to achieve a more precise fit. The thumb hole 311 may be formed by either punching or cutting a corresponding portion from the article 310.

Before actually applying the article 310 to the forearm, a flexible stockinette tube or cast padding 330 is preferably placed around the patient's forearm to prevent undesirable adhesion or contact between the splint and the patient's forearm. For example, a tubular padding material may be used for this purpose, such as one-sidedly puffed tubular textile fabric made on a sports sock machine available from Broadway Knitting Mills, 2152 Sacramento Street, Los Angeles, Calif. 90021.

The splint of Fig. 5a-d is formed by first activating the resin of article 310 of Fig. 5a with water. Then the thumb of the patient's left or right hand is inserted through the opening 311 and the long edge of the rectangular article is aligned lengthwise along the patient's forearm. Then the article is molded around the forearm and inserted into the in the position shown in Figs. 5b and 5c. In this respect, the resin-impregnated plate has excellent compression formability or conformability to achieve a good fit around the patient's forearm.

The article 310 is sufficiently sized in its longest direction to extend the length of the forearm to be immobilized by the splint. The article 310 is sized in the other direction to allow for swelling of the forearm. This is preferably accomplished by configuring the article 310 to extend partially, but not completely, around the circumference of the forearm. In this regard, and to allow for swelling of the forearm, the orthopedic splint 310 preferably extends about 40% to about 90% of the circumference of the forearm, and most preferably about 60% to about 75% of the circumference of the forearm. This partial enclosure accommodates swelling of the injured forearm while still providing sufficient immobilization to promote healing.

However, it will be appreciated that the splint article could also be circumferentially configured to completely surround the forearm if desired. To accommodate swelling in such a case, it is important that a longitudinal gap be left in the splint article. While these are not the currently preferred embodiments, the splint article could thus be wrapped around the forearm merely until the longest edges come very close to or even touch each other (without firmly bonding the edges together), or alternatively so that the longest edges actually overlap slightly, but again without firmly bonding the edges together, so that the splint could still expand and thus make room for swelling. Means of preventing the edges from firmly bonding include the use of a non-adhesive layer inserted between the overlapping edges.

The orthopedic splint article 310 is preferably held in place by means of fasteners while the resin cures. For example, wrapping devices such as the stretch bandage 340 shown in Figure 5d can be used to secure the article 310 around the forearm during curing so that the resulting orthopedic splint conforms snugly to the forearm. Although a right arm is shown, it should be understood that the splint article 310 can be applied to a left arm just as well.

Once applied, the article 310 can be easily adjusted or repositioned during curing (but before the resin hardens) without significant wrinkling. Furthermore, after curing, and after the splint has served its intended purpose, the splint can be removed from the patient's forearm by unwinding the stretch bandage and then prying the splint open. The general U-shape of the forearm splint 310 shown in Figures 5a-d has been found to provide excellent strength and fracture resistance.

Briefly, the orthopedic splint article 310 of the present invention can be applied to a forearm by: (1) exposing the article to water to initiate curing of the resin, (2) manually squeezing out excess water, (3) appropriately positioning the orthopedic splint article over a stockinette or cast pad that has been applied to the forearm, (4) cutting the orthopedic splint to the desired shape, and (5) holding the splint in place while the resin cures, e.g., by wrapping a stretch bandage or other fastener around the splint article and forearm to hold the splint in place.

If desired, the splint articles of the present invention may include fillers or other additives. Suitable fillers for use in the present invention include inorganic or organic particulate or fibrous materials as described in U.S. Patent Application No. 08/463,993. Colored pigment fillers and mixtures of fillers may also be suitable.

Preferred particulate fillers have an average particle diameter of less than 500 µm, more preferably less than 200 µm, and most preferably less than 120 µm. As used herein, the term "average particle diameter" is defined as the diameter of a sphere having the same volume as the particle.

Microfibers (as described in U.S. Patent Application Nos. 08/248,341 and 08/008,755) may be added to the resin to increase the integrity of the web or the strength of the composite. Preferred fibers have an average length between 25 and 5000 µm, more preferably between 30 and 1000 µm, and most preferably between 30 and 500 µm.

Preferred fillers and microfibers for use with water-curable resins also have a very low moisture content. Preferably, the filler or microfiber contains less than 4% absorbed water by weight, more preferably less than 1% absorbed water by weight, and most preferably less than 0.5% absorbed water by weight. The amount of absorbed water in a filler or microfiber sample can be determined by heating the sample in an oven and measuring the weight loss of the sample. Fillers or microfibers that have a high moisture content are preferably dried before incorporation into the resin.

If desired, the fillers or microfibers can be surface treated using silanes, titanates, zirconates and the like to enhance bonding with the resin, easy miscibility and compatibility. The surface treatment can be done before incorporation of the filler or microfiber into the resin or in situ, i.e. the surface treatment agent can be incorporated into the resin for later reaction with the filler.

The storage stability of the uncured casting material is an important consideration in selecting appropriate ingredients. "Storage stability" refers to the ability of the finished product to resist degradation under normal storage conditions. For example, for products comprising isocyanate-functional polyurethane prepolymers, these standard storage conditions would include storage in a moisture-free environment at 25ºC. The storage stability of a casting material preferably exceeds 1 year when kept at room temperature (i.e., 25ºC); more preferably, the storage stability exceeds 3 years, and most preferably, the storage stability exceeds 5 years. The storage stability of a casting material containing a curable resin may also be tested at elevated temperature (49ºC) to predict stability at room temperature. Preferred casting materials will withstand four weeks at 49ºC, highly preferred casting materials will withstand eight weeks at 49ºC, and most preferred casting materials will withstand twelve weeks at 49ºC.

Notably, many commercially available fillers, such as glass bubbles, are basic (i.e., alkaline) and can cause undesirable side reactions in isocyanate-functional polyurethane prepolymers. These side reactions can cause the resin to cure prematurely or prevent curing altogether. Preferred optional fillers are chosen so that the storage stability of the resin material is not compromised. When isocyanate-functional polyurethane prepolymer systems are used, it is desirable to ensure that the optional fillers are neither basic nor contain basic impurities. Such basicity can cause side reactions (such as trimerization, allophonate formation, and biuret formation) in the isocyanate-functional resin system, which can limit the storage stability of the product. Adverse effects of filler basicity can be minimized by washing and/or neutralizing the filler with an appropriate acid or by adding an acidic stabilizer to the resin.

For decorative purposes, resin systems can also be colored using dyes or pigments or both. Luminescent pigments can also be used. Alternatively, the splint or cast of the present invention can be wrapped with a decorative or informative film comprising raised letters and/or numbers that can leave impressions in the material. Furthermore, the materials of the present invention can be printed using suitable dyes or pigments by direct or indirect printing processes such as transfer printing, pigment printing or inkjet printing.

Conveniently, colour may be used to demarcate the "soft area" from the "hard area". For example, the soft resin may be coloured in a distinct way so that it is visibly different from the hard resin. Alternatively, part of the carrier fabric may be coloured to demarcate the soft and hard areas. In both cases, the different colours may facilitate alignment of the soft area if desired.

A fugitive water-soluble mesh, as described in U.S. Patent Application No. 08/404,242, may be used as a release layer separating adjacent layers of the tape from each other (e.g., when the tape is provided as a roll).

The following examples are intended to facilitate an understanding of the present invention and are not intended to limit the scope thereof. Unless otherwise indicated, all parts and percentages are by weight.

Examples example 1 Casting articles that include a hard central area and two soft peripheral areas of different widths

A fiberglass fabric was knitted according to the process described in U.S. Patent No. 4,609,578. The fiberglass fabric was 7.938 cm (3 1/8 inch) wide and had 41 courses of ECDE 75-1/0 fiberglass yarn.

Casting tapes used as samples were prepared by coating the resulting fabric with two different liquid isocyanate-terminated polyurethane prepolymer resins. A first resin was a "hard resin" as described in Table 1a. A second resin was a "soft resin" as described in Table 1b. Table 1a "hard resin"³

¹ "DMDEE" = 2,2'-dimorpholinodiethyl ether

² "Arcol 24-32" = polymer-filled polyol

³ The combined components result in an NCO to OH ratio of approximately 4.0. Table 1b "soft resin"²

¹ "MEMPE" = morpholinoethyl morpholino isopropyl ether

² The combined ingredients result in an NCO to OH ratio of 3.0.

Coating was accomplished using a three-part slot die that directed the first and second resins to the center and edge regions of the casting tape, respectively. See Figures 8a-d. Alternatively, the modified coating apparatus described in copending U.S. Patent Application Serial No. 08/672,014, "Die for Extruding Multiple Fluid Streams," may be used. The coated casting tape had about 43.5 wt.% resin.

The central, longitudinally extending portion of the casting tapes was coated with a first, "hard" resin. The two longitudinally extending edge portions of the casting tapes were coated with a second, "soft" resin in five different widths as shown in Table 1c. Two control casting tapes were prepared using the same type of fiberglass fabric, but with either the soft resin (Control "S") or the hard resin (Control "H") coated across the full width of the tape. Table 1c

Ring strength was measured as described in the following procedure. A cylindrical ring comprising 6 layers of the resin-coated material was formed by removing a roll of the resin-coated material from its storage bag and completely immersing the roll in water at a temperature of about 27ºC for about 30 seconds. The width of the ring formed was the same as the width of the resin-coated material used, namely 7.938 cm. The roll of resin-coated material was then removed from the water and the material was wrapped around a 5.08 cm diameter mandrel covered with a thin stockinette tube (such as 3M Synthetic Stockinet MSO₂) to form 6 complete uniform layers using a controlled wrapping tension of about 45 g per cm of the width of the material. Each cylinder was completely wrapped within 30 seconds of removal from the water.

Approximately 20 minutes after the first water immersion, the cured cylinder was removed from the mandrel. The ring strength was determined 24-72 hours after the first water immersion, i.e. the samples were allowed to cure for at least 24 hours in a controlled atmosphere of 25ºC ± 2ºC and 55% ± 5% relative humidity prior to testing.

Then, at the appropriate time, each cylinder was placed in a fixture in a commercial testing machine, such as an Instron instrument, and compression loads were applied to the cylindrical ring specimen along its outside and parallel to its axis. The cylindrical ring was placed lengthwise between the two lower bars of the fixture (the bars were 1.9 cm wide, 1.3 cm high, and 15.2 cm long), with the bars approximately 4 cm apart. The inside edges of the bars were machined to create a curved surface with a radius of 0.31 cm. Then a third bar (0.63 cm wide, 2.5 cm high, and 15.2 cm long) was centered over the top of the cylinder and also parallel to its axis. The lower, contacting edge of the third bar was machined to create a curved surface with a radius of 0.31 cm. The third rod was pushed down so that it pressed against the cylinder at a rate of about 5 cm/min, crushing it. The maximum force exerted in crushing the cylinder was then recorded as the "ring strength", which in this particular case is the "dry strength" (expressed as force per unit length of cylinder, ie in Newtons/cm). At least 5 samples were tested for each material and then the mean maximum force exerted was calculated and reported as the dry "ring strength". The results of the ring strength tests are shown in Table 1d. Table 1d

The above data suggest that hoop strength is related to the amount of soft resin at the edges. In general, hoop strength decreases as the width of the soft edges increases. However, acceptable hoop strength can be achieved even if both edges of the tape comprise soft resin. It should also be noted that for a significant portion of a wrapped cast, the soft region will overlap a hard region of an adjacent layer. Presumably, casts made from the above tapes with the two resins, when wrapped around a limb, will provide more than sufficient strength to immobilize a fracture.

Preferred casting products of the present invention have a hard central region comprised of a material having a hoop strength of greater than 70 N/cm, more preferably greater than 80 N/cm, and most preferably greater than 100 N/cm. Preferred casting products of the present invention have a total hoop strength of greater than 70 N/cm, more preferably greater than 80 N/cm, and most preferably greater than 100 N/cm.

Ring delamination was measured as described in the following procedure. A cylindrical ring comprising 6 layers of the resin coated material was formed by removing a roll of the resin coated material from its supply bag and completely immersing the roll in water at a temperature of about 27°C for about 30 seconds. The width of the ring formed was the same as the width of the resin coated material used, namely 7.938 cm. The roll of resin coated material was then removed from the water and the material was wrapped around a 5.08 cm diameter mandrel covered with a thin stockinette tube (such as 3M Synthetic Stockinet MSO₂) to form 6 complete uniform layers using a controlled winding tension of about 45 g per cm of the width of the material. At the end, a piece of about 15.24 cm was left exposed, and the rest of the roll was cut off. Each cylinder was completely wound within 30 seconds of being removed from the water.

Fifteen to 20 minutes after the first water immersion, the cured cylinder was removed from the mandrel and its delamination strength was determined 30 minutes after the first water immersion.

Delamination strength was determined by clamping the free end of the cylindrical sample in the jaws of the testing machine, an Instron Model 1122 machine, and passing a spindle through the hollow core of the cylinder so that the cylinder could rotate freely about the axis of the spindle. The Instron machine was then activated to pull on the free end of the sample at a rate of approximately 127 cm/min. The average force required to delaminate the wrapped layers over the first 33 cm of the cylinder was then recorded as force per unit width of the sample (Newtons/cm width). At least 5 samples were tested for each material and then the average delamination force was calculated and reported as "delamination strength". The results of the delamination strength tests are shown in Table 1e. Table 1e

¹ Typically, the delamination strength for this control cast material would be approximately 7.706 N/cm.

The above data indicate that delamination strength is related to the amount of soft resin. In general, delamination strength may decrease slightly as the width of the soft edges increases. However, delamination strength is still acceptable even when both edges of the tape comprise soft resin. Also, it should be noted that for a significant portion of a wrapped cast, the soft region will overlap a hard region of an adjacent layer. Casts made from the above tapes provide adequate delamination strength when wrapped around a limb.

Preferred casting products of the present invention have a total delamination strength of greater than 4 N/cm, more preferably greater than 5 N/cm, and most preferably greater than 6 N/cm.

Example 2 TABER stiffness of various commercially available cast products

Several commercially available casting tapes were measured as described below to determine their relative TABER stiffness. The stiffness values were obtained using the procedures described in ASTM Standard No. D5342-93 and using a Teledyne Taber V-5 Stiffness Tester (available from Teledyne, Tonawanda, NY).

A single layer of casting material for each specimen was unrolled and laid flat on a sheet of polyethylene film and allowed to cure for approximately 48 hours under ambient conditions (e.g., 30-40% RH and 21ºC). Once cured, the specimens were cut into rectangular specimens 3.81 cm wide and 6.985 cm long using a Teledyne Taber "Triple Cut Shear" (available from Teledyne, Tonawanda, NY). The long side of the specimen was perpendicular to the length of the casting tape, meaning the stiffness values reflect the stiffness values across the web direction of the tapes for casts. Three samples of each specimen were tested. The mean results are shown in Table 2a. Table 2a

¹ Available from Carapace A Lohmann Co., Tulsa, OK.

² Available from Johnson & Johnson, Rayham, MA.

³ Available from Smith and Nephew, Germantown, WI.

&sup4; available from 3M Company, St. Paul, MN.

&sup5; available from Zimmer, Warsaw, IN.

&sup6; The Dynacast Pro and Delta Lite Flashcast casting materials are both examples of casting materials that comprise a typical "hard resin" applied to a relatively low modulus polyester-based backing.

&sup7; Scotchcast softcast casting material is an example of a casting material that comprises a "soft resin" coated on a fiberglass backing. This material is generally described in U.S. Patent No. 4,968,542.

The above data suggest that the overall stiffness of a casting product is related to either the elastic modulus of the carrier fabric or the type of resin used. Preferred casting products of the present invention have at least one soft edge region comprised of a material having a TABER stiffness value of between about 0.01 and 90, more preferably between 5 and 75, and most preferably between 10 and 50. Preferred casting products of the present invention have a hard central region comprised of a material having a TABER stiffness value of greater than 90, more preferably greater than 100, most preferably greater than 150, and optimally greater than 250.

Example 3 Edge stiffness of various cast articles

Several commercially available casting tapes and a casting tape of the present invention were measured as described below to measure their relative edge stiffness.

Edge stiffness was measured as described in the following procedure. A cylindrical ring comprising 3 layers of the resin coated material was formed by removing a roll of the resin coated material from its supply bag and completely immersing the roll in water at a temperature of about 27ºC for about 30 seconds. The width of the ring formed was the same as the width of the resin coated material used. The roll of resin coated material was then removed from the water and the material was wrapped around a 5.08 cm diameter mandrel covered with a thin stockinette tube (such as 3M Synthetic Stockinet MSO₂) to form 3 complete uniform layers using a controlled wrapping tension of about 45 g per cm of the width of the material. Each cylinder was completely wrapped within 30 seconds of removal from the water.

Approximately 20 minutes after the first water immersion, the cured cylinder was removed from the mandrel. Edge stiffness was determined 24-72 hours after the first water immersion, i.e. the samples were allowed to cure for at least 24 hours in a controlled atmosphere of 25ºC ± 2ºC and 55% ± 5% relative humidity prior to testing.

Each cylinder was placed in a fixture in a commercial test machine, such as an Instron instrument. See Figs. 7a and 7b. The fixture supported the rings at a 45º angle to the load plane. Compression loads were applied to the leading edge of the cylindrical ring specimen using a 1.27 cm diameter probe. The position of the specimen and fixture are shown in Fig. 7b.

The testing machine was programmed to compress the leading edge of the sample by 3 mm and then the machine was stopped and a force reading was taken. The maximum force exerted in depressing the edge of the cylinder was then recorded as the "edge stiffness" (expressed as force, i.e. in Newtons). At least 5 samples were tested for each material and then the mean maximum force exerted was reported as the "edge stiffness". The results of these tests are shown in Table 3a. Table 3a

¹ Available from Alcare Co., Japan.

The above data indicate that the edge stiffness of a casting product may be related to either the modulus of elasticity of the backing fabric or the type of resin used. Preferred casting products of the present invention have an edge stiffness value of less than about 20, more preferably less than 10, and most preferably less than 5 when tested as described herein.

Claims (22)

1. Orthopaedic cast bandage comprising: a first longitudinally extending region of a soft casting material; and a second longitudinally extending region of a rigid casting material connected to the first region. 2. An orthopedic casting tape according to claim 1, wherein the casting tape comprises: a carrier; and at least one curable resin associated with the carrier. 3. An orthopedic casting tape according to any preceding claim, wherein the soft casting material comprises a soft curable resin associated with a backing and the hard casting material comprises a hard curable resin associated with a backing. 4. An orthopedic cast bandage according to claim 2, wherein the longitudinally extending portion is made of the soft cast material and the longitudinally extending portion is made of The hard material for casts can include different curable resins. 5. An orthopedic casting tape according to claim 2, wherein the longitudinally extending portion of the soft casting material and the longitudinally extending portion of the hard casting material comprise different backings. 6. The orthopedic casting tape of claim 2, wherein the longitudinally extending portion of the soft casting material and the longitudinally extending portion of the hard casting material comprise different backings and different curable resins. 7. An orthopedic casting tape according to claims 3 to 6, wherein the different curable resins are water-curable isocyanate-functional prepolymers formed by the reaction of an isocyanate and a polyol having an NCO:OH ratio between 1.5:1 and 7:1, wherein a first curable resin is a hard-curable resin having an isocyanate equivalent weight of less than 500 g and an average hydroxy equivalent weight of the polyol of less than 500 g, wherein a second curable resin is a soft-curable resin having an isocyanate equivalent weight of more than 500 g and an average hydroxy equivalent weight of the polyol of more than 500 g. 8. An orthopedic casting tape according to claims 3 to 6, wherein the different curable resins are water-curable isocyanate-functional prepolymers formed by the reaction of an isocyanate and a polyol having an NCO:OH ratio of between 2.5:1 and 4.5:1, wherein a first curable resin is a hard curable resin having an isocyanate equivalent weight of less than 400 g and an average hydroxy equivalent weight of the polyol of less than 400 g, wherein a second curable resin is a soft curable resin having an isocyanate equivalent weight of more than 1000 g and an average hydroxy equivalent weight of the polyol of more than 1000 g. 9. Tape for orthopedic casts according to claims 2 to 8, wherein the carrier is a fiberglass fabric. 10. The orthopedic casting tape of claim 1, wherein the soft casting material comprises a first extruded casting material and the hard casting material comprises a second, different extruded casting material. 11. An orthopedic casting tape according to any preceding claim, wherein the hard casting material has a TABER stiffness value of greater than 90 and the soft casting material has a TABER stiffness value of less than 90. 12. An orthopedic casting tape according to any preceding claim, wherein the hard casting material has a TABER stiffness value of greater than 150, the soft casting material has a TABER stiffness value of between about 5 and 75, and the casting tape has a total hoop strength of greater than 80 N/cm. 13. An orthopedic casting tape according to any preceding claim, wherein the first longitudinally extending portion is between about 0.5 and 4 cm wide. 14. An orthopedic casting tape according to any preceding claim, wherein the first longitudinally extending portion is between about 1 and 3 cm wide and forms a first edge of the casting tape. 15. An orthopedic casting tape according to any preceding claim, wherein the casting tape comprises two longitudinally extending regions of soft casting material each between about 1 and 3 cm wide and forming first and second edges of the casting tape. 16. The orthopedic casting tape of claim 10, wherein the first and second extruded casting materials comprise a thermoplastic polymer that softens or melts at a temperature of less than about 90°C. 17. An orthopedic casting tape according to claim 10, wherein the first and second extruded casting materials comprise a viscous curable material that can be extruded through a nozzle and subsequently gelled to a state where it does not flow for long periods of time at ambient temperatures. 18. Splint articles, comprising: a carrier; and at least one curable resin associated with the carrier, wherein the splint article comprises a hard central region and at least one soft edge region. 19. The splint article of claim 18, wherein the splint further comprises a thumb hole having a soft edge region surrounding the perimeter of the thumb hole. 20. Splint article according to claims 18 and 19, wherein the carrier is selected from the group consisting of knitted, woven or nonwoven fabrics and open-cell foam sheets, wherein the splint comprises two different water-curable isocyanate-functional prepolymer resins and the material of the hard center comprises a TABER stiffness value of more than 90 and the soft edge material has a TABER stiffness value of less than 90. 21. Use of the band for orthopedic casts according to one of claims 1 to 17 or of the splint article according to one of claims 18 to 20 for producing an orthopedic cast. 22. A method for producing a tape for orthopedic casting, comprising the following steps: Providing a textile carrier; and Coating the carrier with two different curable resins, wherein the coated textile carrier is in the form of a casting tape which comprises at least one longitudinally extending region made of a soft casting material and at least one longitudinally extending region made of a hard casting material.